1. Field of the Invention
The present invention relates to seismic signal recording equipment and, more particularly, to a device to test certain performance characteristics of such seismic signal recording equipment.
2. Setting of the Invention
In seismic prospecting for natural resources, such as for hydrocarbons, an energy impulse is imparted to the earth and the resulting reflected energy signals are detected at the earth's surface by vibration sensing devices, such as geophones and hydrophones. The output of these vibration sensing devices are recorded by seismic signal recording equipment for later processing and interpretation. The seismic signal recording equipment often includes the capability for stacking or "summing" of the recorded signals and/or filtering the recorded signals to remove undesirable noise.
To insure that the seismic signal recording equipment is fully operational, periodic testing operations are initiated. In these testing operations, it is important to be able to test all of the performance characteristics of the seismic signal recording equipment, such as the stacking and the filtering functions stated above. One such way to test the performance characteristics of the seismic signal recording equipment is by an actual seismic source initiation and recording of the seismic signals generated thereby. The recorded seismic signals are thereafter compared with recorded signals obtained by a different recording unit at the same location. This testing procedure is both time consuming and expensive; more importantly, from one seismic initiation to another, the seismic signal can vary so that the seismic signal recording equipment's performance characteristics cannot be tested accurately and in a reproducible manner.
Other testing devices and methods have been developed to test the operability of individual geophones or hydrophones, as well as hydrophone and geophone arrays. Some representative testing methods of this type are illustrated in U.S. Pat. Nos. 4,166,270, 4,366,561, 4,320,468 and 4,184,143. None of the above patents disclose or suggest testing seismic signal recording equipment, nor the testing of performance characteristics of such seismic recording equipment. There exists a need for a testing device capable of testing performance characteristics of seismic signal recording equipment quickly, efficiently and in a reproducible manner.